Texture formats overview

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Direct X Texture formats (DXTn) are licensed use of S3 Graphics Ltd S3 Texture Compression (S3TC) technology.

S3TC Format Comparison

S3TC (aka DXTn or DXTC)

DXT4/5 use an interpolated alpha scheme, they generally produce superior results for alpha (transparency) gradients than DXT2/3.
Some consider DXT5 to be the most flexible general purpose compression codec.

FOURCC FS versions Description Alpha premultiplied? Compression ratio Texture Type
DXT1 All ¹ 1-bit Alpha / Opaque N/A 8:1 Simple non-alpha
DXT2 Not supported Explicit alpha Yes 4:1 Sharp alpha
DXT3 All Explicit alpha No 4:1 Sharp alpha
DXT4 Not supported Interpolated alpha Yes 4:1 Gradient alpha
DXT5 FSX only Interpolated alpha No 4:1 Gradient alpha


  • ¹ DXT1 with an alpha may cause transparency issues in FSX SP2 when using pre-FSX objects. In this setting, it is the model material settings that cause the difficulties, rather than the single bit colorkey alpha.
  • For any packages requiring dual FS9 & FSX compatibility, to minimize any transparency issues, recommend using DXT3 type.
  • For conversion utilities, see the Tools section below.

It is important you understand the impact of missing textures, or mis-matched texture file extensions.
Please first read - Texture - Missing (FSX)

DXT Types


DXT1 is a four-bit compressed color format that allows for opaque, and one-bit alpha textures;
that is, textures with no transparency at all, and textures with a single transparent color.

DXT1 is not suitable for gradients, and will result in banding, DXT1 should not be used for glass or props.


DXT3 adds support for a four-bit explicit alpha channel, on top of DXT1's color compression.
Four-bit explicit alpha allows for sixteen distinct alpha values, making it good for textures with sharply contrasting translucent/opaque areas.


DXT5 support a four-bit interpolated alpha channel.
Three bits are used to determine explicit alpha values, and two eight-bit values are used to interpolate gradually between them.
This makes the format especially suited for soft gradients and other textures where the alpha areas vary less wildly.

Further Detail

For further information, please see - DXT compression explained

Alpha Types

INSERT explanation of alpha types, or a link to.

  • 1-bit Alpha - placeholder
  • Explicit alpha - placeholder
  • Interpolated alpha - placeholder
  • Simple non-alpha - placeholder
  • Sharp alpha - placeholder
  • Gradient alpha - placeholder


Tool Description Rating Availability URL
Image Tool Official - All formats manipulation * * * * * SDK SDK Installation (FSX)
DXTBmp 16/24/32 bit and DXT Extended Bitmap Manipulation ²     * * * * * Freeware Click button at foot of page (SizeMb)
Tool Name Descriptive blurb ????? Payware Download Page (SizeMb)
ColorPix Colour grabbing tool. * * * * * Freeware Download Page (SizeMb)
  • ² DXTBmp - This info is only for FSX BMP to DDS. You must flip the image with DXTBmp before you convert it to DDS. If you want to use bmp you don't need to flip it.
  • ColorPix - Useful for colour-matching when correcting overlaid transparency issues.




  • Direct3D - Exposes the advanced graphics capabilities of 3D graphics hardware, including z-buffering, anti-aliasing, alpha blending, mipmapping, atmospheric effects, and perspective-correct texture mapping.
  • Bump Mapping - A technique to add details to shading without using more polygons.
  • Normal Mapping - An enhancement of bump mapping.
  • DirectDraw Surface - Wikipedia (aka .dds) - A file format used for storing textures and cubic environment maps, both compressed and uncompressed.
  • DirectDraw Surface - MSDN (aka .dds) - A file format used for storing textures and cubic environment maps, both compressed and uncompressed.
  • 3Dc - A lossy data compression algorithm for normal maps invented and first implemented by ATI. It builds upon the earlier DXT5 algorithm and is an open standard. 3Dc is now implemented by both ATI and NVIDIA.